Watch Cast Away. When he's on the raft the paddle washes away. Later when he hits the rocks he crawls out of the raft and it floats away as he's climbs on shore. But when he wakes up he's lying on the raft, the paddle is in his hands and the patch of rocks is nowhere to be seen!
Apparently, you didn't actually watch the movie.
First of all, the paddle is tied to the raft. This is seen when Chuck first gets into it after swimming away from the exploding engine.
Second, he never got out of the raft when he washed up against the rocks. All he did was peek over to look at the island. Obviously, he didn't want to actually get out of the raft for numerous reasons: 1) he didn't know how deep the water was, 2) were the rocks sharp and dangerous, etc. The tied, over the course of a night, could very well, take him off the rocks where he was and eventually deposit him back onto a back elsewhere.
The paddle is attached to the raft by a rope, he never threw it away…he just tossed it to the side. It doesn't look to me like he got completely out of the raft when he hit the rocks. Looks like he just crawled half way out leaving his legs in the raft. Of course that could just be my assumption because that's what I would have done in his place. It's pretty obvious to me that the rocks are jutting out into the ocean and he's seeing the island from them then he just floats to shore.